A standard roller bearing has an annular inner race centered on an axis and formed with a radially outwardly directed inner annular race surface, an annular outer race surrounding the inner race and having an inwardly directed outer race surface concentric with the inner surface, at least one annular row of rollers engaging both of the surfaces, and an annular cage formed with respective radially open windows for the rollers. The rollers may be balls, cylinders, or crowned cylinders known as barrels. With ball and barrel rollers the race surfaces are of a curvature complementary to the rollers and with cylindrical rollers these surfaces are cylindrical.
It is normally considered preferable to employ one-piece or unitary races and cages. When of such construction the races are stronger and their race surfaces are smooth and initerrupted by a seam. With a one-piece cape the webs between the windows can be reduced to a minimal angular width so that the maximum number of rollers can be used, thereby minimizaing loading of the bearing.
In many applications use of unsplit or one-piece bearings is impossible. This is the case where axial access to the bearing location is limited, or where a machine would have to be largely disassembled to pull the shaft and replace the bearing. In addition in very large applications, as with shafts of, say, one meter or more in diameter, it is impossible to use such an unsplit bearing.
Hench recourse is has to so-called split-ring bearings. Such a bearing simply has its two races and cage each formed of two or more generally identical parts that can be assembled to form the respective parts. Thus on a large shaft needing a new bearing the bearing location is uncovered on one side and the old bearing is disassembled or cut off. The inside race is then assembled on and clamped by its holding rings on this shaft. One part of the outer race is fitted to the machine housing, and then the cage parts each carrying the respective roller are assembled around inner race. Finally the outer-race part or parts are secured around the rollers and cage to the installed outer-race part, and the machine is closed up. Such a procedure does not require the shaft to be pulled or axially displaced at all relative to its housing. All that is needed is a small amount of radial movability of the shaft at the bearing location.
A principal disadvantage of such split roller bearings, as discussed in the publication Walzlagertechnik (p. 2ff, 1979-1, Firma FAG Kugelfischer Georg Schafer & Co.), is that they cannot use as many rollers as unsplit bearings of the same size. Thus they inherently must be rated for smaller loads and lower operating speeds. This is due to the necessity of providing a minimal web dimension around each roller window, so that at each joint between two cage parts this circumferential dimension must be doubled, thereby taking up space that could otherwise be occupied by a roller.
It has been suggested to eliminate the cage between the rollers, and to support the rollers by pins carried on washers axially flanking the row of rollers. This necessitates machining pivot holes in the roller ends, and makes fitting the bearing together quite tricky.